Two-Stage Programming (2SP) is an experimental programming language, the first implementation of the Specification-Consistent Coordination Model (SCCM). The SCCM proposes a new, mixed-paradigm (functional/imperative) approach to developing reliable programs based on complete run-time checking of computations with respect to a given specification. A 2SP program consists of a functional specification and an imperative coordination tightly connected to the specification. The coordination maps the specification to an imperative and possibly parallel/distributed program. Normal termination of a 2SP program execution implies the correctness of the computed results with respect to the specification, for that execution. We present the basic feautures of the SCCM/2SP, a new message-spassing system of 2SP with integrated run-time checking, and a larger case study. We show that 2SP provides: functional specifications, specification-consistent imperative coordinations, automatic run-time result verification and error detection, enhanced debugging support, and good efficiency.
